1. Field of the Invention
This invention relates to a non-azeotropic refrigerant for a passive heat pump.
2. Description of the Related Art
U.S. Pat. No. 3,789,621 issued 1974 to Inuzuka discloses a single stage air-to-air heat pump comprising a refrigeration circuit with a compressor, a coil disposed in a first passageway extending between the inside of a building and the outside environment, and a second coil disposed in a second passageway extending between the inside of a building and the outside environment. Inside air is passed over the first coil and then exhausted to the outside and outside air is passed over the second coil and then admitted to the inside. The pumping direction of the compressor may be selected so that the heat pump acts either to heat or cool air entering the building.
More recently, experimental work has been done on a two-stage heat pump system comprising a passive stage and an active stage. The passive stage may comprise an array of heat pipes, that is, closed pipes partially filled with pure refrigerant. The active stage comprises a compressor and coils. Again there are two passageways between the outside and inside of a building One end of the heat pipe array is disposed in one of the passageways and the other end in the other passageway and the pipe array is tilted so one end is higher than the other. Similarly, one coil of the active heat pump is disposed in one passageway and the other coil is disposed in the other passageway. Air from the outside enters through one of the passageways, passes over one end of the heat pipe array and then one of the coils into the inside. Air from the inside passes over the other end of the heat pipe array and then the other coil to the outside. By choosing which end of the heat pipe array is the higher end and the direction of the compressor, this two stage heat pump may either heat or cool air entering the building. The system was also tested with an electric heater in the passageway admitting air to the inside. It was found that the electric heater was mandatory where the outside temperature dipped to -25 degrees C. or less for extended periods since without the heater the admitted air was too cold. This experimental two-stage heat pump system is discussed in Linton, J. W. "A Comparison of Ventilation Strategies for R-2000 Houses" NRC No. 25463, TR-LT-004, National Research Council of Canada, 1986 and Linton, J. W. "Design, Construction, and Testing of an Exhaust Air Heat Pump for R-200 Homes" NRC No. 27719, TR-LT-013, National Research Council of Canada, 1987.
Non-azeotropic refrigerants have been contemplated for an active heat pump and it has been found that some mixtures hold promise, while other mixtures, such as a mixture of R22 and R152a, degrade performance. (See Sami, S. M. "Non-azeotropic Mixtures as Potential CFC Substitutes for Heat Pumps" Proceedings of the International Conference on Heat Pumps in Cold Climates Aug. 13-14, 1990, Moncton, N. B., Canada, pages 141-152.)
There remains a need for a more efficient heat pump, especially for cold climates, which may still admit outside air and exhaust inside air so as to maintain a healthy inside environment.